Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi. I'm Brian and I'll try to help.
You cannot transfer a Microsoft 365 subscription between accounts. You can open a second subscription for the other account, if it's actually a separate account and not just an alias of the first account (and it sounds like it is a separate account). There are less-expensive subscriptions if you just need more space. Microsoft 365 Basic, for example, is only US $20 per year and gets you a 100GB OneDrive quota and a 50GB mailbox quota.